Default Installation of Google Talk doesn’t allow you to login with two different Ids from a single computer. But you can run two different instance of Google Talk at same time on a single computer after tweaking it a little. Just locate the Google Talk shortcut in Start -> Programs -> Google Talk -> Google Talk. Right click on the shortcut and go to properties. A dialog box will open as shown in the image below.
Add “/nomutex” at the end of Target string, it should look like as shown in the image and click ok. That’s all now every time when you want an extra instance of Google Talk, click on this shortcut. Easy!